XGBoostUtils.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package hivemall.xgboost;

import ml.dmlc.xgboost4j.LabeledPoint;

import java.util.List;

public final class XGBoostUtils {

    private XGBoostUtils() {}

    /** Transform List<String> inputs into a XGBoost input format */
    public static LabeledPoint parseFeatures(double target, List<String> features) {
        final int size = features.size();
        if(size == 0) {
            return null;
        }
        final int[] indices = new int[size];
        final float[] values = new float[size];
        for(int i = 0; i < size; i++) {
            if(features.get(i) == null) {
                continue;
            }
            final String str = features.get(i);
            final int pos = str.indexOf(':');
            if(pos >= 1) {
                indices[i] = Integer.parseInt(str.substring(0, pos));
                values[i] = Float.parseFloat(str.substring(pos + 1));
            }
        }
        return LabeledPoint.fromSparseVector((float) target, indices, values);
    }

}